The field of the invention generally relates to air conditioning, and more particularly relates to apparatus for accurately thermostating the operation of an air conditioner.
As is well known, it is common to provide a main partition in an air conditioner with the evaporator being on the room side of the partition, and the condenser and compressor being on the outside. In a typical prior art configuration, an evaporator blower is positioned to one side of the evaporator, and an air intake chamber is located in front of the evaporator blower. In operation, the evaporator blower draws air from the room in through the air intake chamber, and recirculates it through the evaporator back to the room.
It is also common to provide air conditioners with a thermostat control. More specifically, when a temperature sensor gets down to a particular temperature as determined by the thermostat setting, the control turns off the evaporator blower, condenser fan, and compressor. Then, after the temperature of the sensor rises a predetermined amount, the control turns the evaporator blower, condenser fan, and compressor back on for another thermostating cycle. The desired result of these thermostating cycles is, of course, to maintain the room at a fairly constant predetermined temperature. Conventionally, a thermostat bulb has been used to sense the temperature, and it is connected by a capillary tube to a pressure sensitive switch which is mounted on the control panel. In a standard prior art configuration, the thermostat bulb is positioned in the air intake chamber.
It is also well known that it is desirable to be able to introduce fresh air from the outside to mix with the recirculating room air. In fact, for certain specified applications such as, for example, nursing homes, federal regulations require that fresh air constitute at least 20% of the rated evaporator air. Generally, fresh air is introduced through a vent in the partition between the room side and the outside. The vent is provided with a door. When the door is closed, only room air is circulated. However, when the door is open and the fan is activated, fresh air is drawn through the vent in the partition and it mixes with recirculating room air before being directed through the evaporator.
It has been found that with the above-described air conditioner arrangement, there can be a tendency for the air conditioner to short cycle. That is, the air conditioner may cycle back on before there is a sufficient delay, and such operation may cause a relatively high compressor failure rate. Also, it has been found that the room temperature has not been closely controlled or regulated.